Chromosome structural stability but canalized anphiplastia in AABB allotetraploids of Arachis

SEIJO G.; CHALUP L; SAMOLUK S.; FÁVERO AP; ROBLEDO G.

Brisbane

Conferencia; Eighth International Conference of the Peanut Research Community- Advances in Arachis through Genomics & Biotechnology; 2015

THE INTERNATIONAL PEANUT GENOME INITIATIVE

Allopolyploidyis an important evolutionary mechanism in plants. Numerous genetic and epigenetic mechanismshave been shown to generate the wide range of structural and functional genomemodifications associated with merged genomes arising from polyploidy events.However, to date little is known about the genome interactions that occurred inthe AABB tetraploids of Arachis. Inthis report, we cytologically analyzed three AABB polyploids: the cultivatedpeanut, thewild A. monticola [both withspontaneous origin (A. duranensis x A. ipäensis) 4x] and one reciprocal syntheticamphidiploid (A. ipäensis x A. duranensis)4x. Thepatterns (number and position) of heterochromatic DAPI+ bandsand the 45S and 5S rDNA mapped by FISH were highly conserved among the polyploidsand exactly reproduced the sum of those observed in the diploid progenitors. Telomericprobes hybridized always at the end of the chromosomes and did not reveal anystructural rearrangement. Moreover, the occurrence of intergenomictranslocation was not evidenced by GISH analysis. However, in the threepolyploids analyzed the activation of the NORs was biased in favor of thosebelonging to the A genome (A. duranensis).Our results showed a clear pattern of additivity with a strong structuralquiescence at the chromosome level. However, the pattern of rDNA activationdemonstrates that rapid functional changes occurred in the AABB allopolyploids,which involve the differential inactivation of the B genome nucleolarorganizing regions (NOR). Moreover, the differential inactivation of the Bgenome NORs occurred irrespective of the species that acted as maternal donor,suggesting a canalized epigenetic control of these loci.